Um, you checked with the gate 1 time when you first got there...they told you they do not know how long the flight would be delayed...they and the boards just said delayed. You took it upon yourself to leave the gate area and not check back in with the gate for a flight that was delayed, but no one knew how long the delay was. Could have been 10 minutes, could have been 2 hours.
No boarding announcements??? How on earth did everyone else know when to board? Could it have been that they heard a boarding announcement and you did not? Did the plane leave with no one on board because no boarding announcement was made?
I don't think so.
Unsympathetic? Damn right! There are 100-150 people on the average flight. Its and airline, not a babysitting service. It is your responsibility to get your self where you need to be. It is your responsibility to be within earshot of announcements. Announcements are not made in bars and restaurants, only in the gate area and the terminal. Airlines do not board at restaurants and bars, they board at the gate. That is where you should have been along with everyone else who did get on the flight.
Take some responsibility for yourself and stop blaming others.